1. Field of the Invention:
This invention relates generally to a display emulating system and, more particularly, to a system capable of emulating different display units, that is, executing a program prepared for another display to imitate means for controlling another display.
The term "emulation" is generally defined as a technique for executing programs which are developed for other computers or systems having different architecture.
The emulation technique is used, for example, when it is desirable for a computer or a system to use a program prepared for another computer or another system having a different architecture. The emulation is also useful in such a case where compatibility should be maintained even after the architecture has been changed. A display emulating system according to the present invention emulates various kinds of displaying means such as a monitor, a plasma display and a liquid crystal display (LCD) wherein the resolutions and controlling methods thereof are different from each other.
2. Prior Art
The prior art will be described in taking the case of a panel display, for example a liquid crystal display.
FIG. 1 is a block diagram of a panel display system in the prior art. In FIG. 1, a display controller section 17 includes a panel controller 1 which is connected to a system bus 1a through an address bus 1b and a command bus 1c. The panel controller 1 is also connected to the system bus 1a through a data buffer 2 which is connected to the system bus 1a and the panel controller 1 through a system data bus 1d and a data bus 2a, respectively. The panel controller 1 controls the operation of a panel display 3 through a panel interface buffer 8 which receives panel data 8a from the panel controller 1 and sends interface signals 8b to the panel display 3. A clock signal for the panel controller 1 is provided by a crystal 4. The display controller section 17 further includes a video memory 5, a character generator 6 and a data controlling circuit 7. The video memory 5 and the data controlling circuit 7 are controlled by a memory control signal 5a and a data control signal 7a, respectively. An address signal and data are transmitted through a memory address/data bus 5b among the panel controller 1, video memory 5, character generator 6 and data controlling circuit 7. Character data generated by the generator 6 are transferred to the panel controller 1 under control of the circuit 7. In order to store data for controlling the display operation, the panel controller 1 is provided with a group of internal registers 20.
In operation, control data prepared so as to satisfy the specification of the panel display 3 are stored in the internal registers 20 within the panel controller 1. The control data comprises, for example, the number of rows able to be displayed, the number of columns able to be displayed, the number of dots arranged in rows and columns usable for display, the position of a cursor and the shape of a cursor.
The control data are set up using a program such as an application software or a system software and are transmitted to the panel controller 1 through the system bus 1a. The panel controller 1 receives the control data through the address bus 1b, command bus 1c and data bus 2a, and stores such data in the internal registers 20. The data to be displayed on the panel display 3 are inputted into the panel controller 1 through the data bus 2a, address bus 1b, and command bus 1c, and then written in predetermined locations within the video memory 5 through the memory address/data bus 5b.
In the displaying operation, the panel controller 1 controls the operation in accordance with the contents stored in the internal registers 20. First, the data stored at an address 0 (zero) of the video memory 5 are read out on the memory address/data bus 5b in accordance with the memory control signal 5a. Such data are changed to the character data 6a by the character generator 6, and then returned to the panel controller 1 through the data controlling circuit 7. The panel controller 1 further modifies the received data to generate the panel data 8a which are further changed by the panel interface buffer 8 to the interface signals 8b to be displayed on the panel display 3. The operation of the reading out of the data, modifying the data and outputting the modified data is repeated until the address is increased from zero to the location which is the last of a complete image. The image is refreshed by repeating the operation of displaying the image, whereby the display function is carried out.
A panel control signal for controlling the panel display 3 is produced on the basis of the control data stored in the registers 20 and transmitted as the interface signals 8b through the panel interface buffer 8.
Since panel display system in the prior art are thus constructed, the internal registers 20 within the panel controller 1 must be set up so as to correspond to the specification of a panel display each time the program is replaced with another in order to obtain a desirable display operation. If the contents of the internal registers 20 are directly rewritten by an application software such that unsuitable control data are stored in the registers, an appropriate display cannot be carried out.